python实现的DES加密算法和3DES加密算法实例

本文实例讲述了python实现的DES加密算法和3DES加密算法。分享给大家供大家参考。具体实现方法如下：

#############################################################################
#         Documentation          #
#############################################################################
# Author:  Todd Whiteman
# Date:   16th March, 2009
# Verion:  2.0.0
# License: Public Domain - free to do as you wish
# Homepage: http://twhiteman.netfirms.com/des.html
#
# This is a pure python implementation of the DES encryption algorithm.
# It's pure python to avoid portability issues, since most DES 
# implementations are programmed in C (for performance reasons).
#
# Triple DES class is also implemented, utilising the DES base. Triple DES
# is either DES-EDE3 with a 24 byte key, or DES-EDE2 with a 16 byte key.
#
# See the README.txt that should come with this python module for the
# implementation methods used.
#
# Thanks to:
# * David Broadwell for ideas, comments and suggestions.
# * Mario Wolff for pointing out and debugging some triple des CBC errors.
# * Santiago Palladino for providing the PKCS5 padding technique.
# * Shaya for correcting the PAD_PKCS5 triple des CBC errors.
#
"""A pure python implementation of the DES and TRIPLE DES encryption algorithms.
Class initialization
--------------------
pyDes.des(key, [mode], [IV], [pad], [padmode])
pyDes.triple_des(key, [mode], [IV], [pad], [padmode])
key   -> Bytes containing the encryption key. 8 bytes for DES, 16 or 24 bytes
    for Triple DES
mode  -> Optional argument for encryption type, can be either
    pyDes.ECB (Electronic Code Book) or pyDes.CBC (Cypher Block Chaining)
IV   -> Optional Initial Value bytes, must be supplied if using CBC mode.
    Length must be 8 bytes.
pad   -> Optional argument, set the pad character (PAD_NORMAL) to use during
    all encrypt/decrpt operations done with this instance.
padmode -> Optional argument, set the padding mode (PAD_NORMAL or PAD_PKCS5)
    to use during all encrypt/decrpt operations done with this instance.
I recommend to use PAD_PKCS5 padding, as then you never need to worry about any
padding issues, as the padding can be removed unambiguously upon decrypting
data that was encrypted using PAD_PKCS5 padmode.
Common methods
--------------
encrypt(data, [pad], [padmode])
decrypt(data, [pad], [padmode])
data  -> Bytes to be encrypted/decrypted
pad   -> Optional argument. Only when using padmode of PAD_NORMAL. For
    encryption, adds this characters to the end of the data block when
    data is not a multiple of 8 bytes. For decryption, will remove the
    trailing characters that match this pad character from the last 8
    bytes of the unencrypted data block.
padmode -> Optional argument, set the padding mode, must be one of PAD_NORMAL
    or PAD_PKCS5). Defaults to PAD_NORMAL.

Example
-------
from pyDes import *
data = "Please encrypt my data"
k = des("DESCRYPT", CBC, "\0\0\0\0\0\0\0\0", pad=None, padmode=PAD_PKCS5)
# For Python3, you'll need to use bytes, i.e.:
#  data = b"Please encrypt my data"
#  k = des(b"DESCRYPT", CBC, b"\0\0\0\0\0\0\0\0", pad=None, padmode=PAD_PKCS5)
d = k.encrypt(data)
print "Encrypted: %r" % d
print "Decrypted: %r" % k.decrypt(d)
assert k.decrypt(d, padmode=PAD_PKCS5) == data

See the module source (pyDes.py) for more examples of use.
You can also run the pyDes.py file without and arguments to see a simple test.
Note: This code was not written for high-end systems needing a fast
   implementation, but rather a handy portable solution with small usage.
"""
import sys
# _pythonMajorVersion is used to handle Python2 and Python3 differences.
_pythonMajorVersion = sys.version_info[0]
# Modes of crypting / cyphering
ECB =  0
CBC =  1
# Modes of padding
PAD_NORMAL = 1
PAD_PKCS5 = 2
# PAD_PKCS5: is a method that will unambiguously remove all padding
#      characters after decryption, when originally encrypted with
#      this padding mode.
# For a good description of the PKCS5 padding technique, see:
# http://www.faqs.org/rfcs/rfc1423.html
# The base class shared by des and triple des.
class _baseDes(object):
  def __init__(self, mode=ECB, IV=None, pad=None, padmode=PAD_NORMAL):
    if IV:
      IV = self._guardAgainstUnicode(IV)
    if pad:
      pad = self._guardAgainstUnicode(pad)
    self.block_size = 8
    # Sanity checking of arguments.
    if pad and padmode == PAD_PKCS5:
      raise ValueError("Cannot use a pad character with PAD_PKCS5")
    if IV and len(IV) != self.block_size:
      raise ValueError("Invalid Initial Value (IV), must be a multiple of " + str(self.block_size) + " bytes")
    # Set the passed in variables
    self._mode = mode
    self._iv = IV
    self._padding = pad
    self._padmode = padmode
  def getKey(self):
    """getKey() -> bytes"""
    return self.__key
  def setKey(self, key):
    """Will set the crypting key for this object."""
    key = self._guardAgainstUnicode(key)
    self.__key = key
  def getMode(self):
    """getMode() -> pyDes.ECB or pyDes.CBC"""
    return self._mode
  def setMode(self, mode):
    """Sets the type of crypting mode, pyDes.ECB or pyDes.CBC"""
    self._mode = mode
  def getPadding(self):
    """getPadding() -> bytes of length 1. Padding character."""
    return self._padding
  def setPadding(self, pad):
    """setPadding() -> bytes of length 1. Padding character."""
    if pad is not None:
      pad = self._guardAgainstUnicode(pad)
    self._padding = pad
  def getPadMode(self):
    """getPadMode() -> pyDes.PAD_NORMAL or pyDes.PAD_PKCS5"""
    return self._padmode
  def setPadMode(self, mode):
    """Sets the type of padding mode, pyDes.PAD_NORMAL or pyDes.PAD_PKCS5"""
    self._padmode = mode
  def getIV(self):
    """getIV() -> bytes"""
    return self._iv
  def setIV(self, IV):
    """Will set the Initial Value, used in conjunction with CBC mode"""
    if not IV or len(IV) != self.block_size:
      raise ValueError("Invalid Initial Value (IV), must be a multiple of " + str(self.block_size) + " bytes")
    IV = self._guardAgainstUnicode(IV)
    self._iv = IV
  def _padData(self, data, pad, padmode):
    # Pad data depending on the mode
    if padmode is None:
      # Get the default padding mode.
      padmode = self.getPadMode()
    if pad and padmode == PAD_PKCS5:
      raise ValueError("Cannot use a pad character with PAD_PKCS5")
    if padmode == PAD_NORMAL:
      if len(data) % self.block_size == 0:
        # No padding required.
        return data
      if not pad:
        # Get the default padding.
        pad = self.getPadding()
      if not pad:
        raise ValueError("Data must be a multiple of " + str(self.block_size) + " bytes in length. Use padmode=PAD_PKCS5 or set the pad character.")
      data += (self.block_size - (len(data) % self.block_size)) * pad
    elif padmode == PAD_PKCS5:
      pad_len = 8 - (len(data) % self.block_size)
      if _pythonMajorVersion < 3:
        data += pad_len * chr(pad_len)
      else:
        data += bytes([pad_len] * pad_len)
    return data
  def _unpadData(self, data, pad, padmode):
    # Unpad data depending on the mode.
    if not data:
      return data
    if pad and padmode == PAD_PKCS5:
      raise ValueError("Cannot use a pad character with PAD_PKCS5")
    if padmode is None:
      # Get the default padding mode.
      padmode = self.getPadMode()
    if padmode == PAD_NORMAL:
      if not pad:
        # Get the default padding.
        pad = self.getPadding()
      if pad:
        data = data[:-self.block_size] + \
            data[-self.block_size:].rstrip(pad)
    elif padmode == PAD_PKCS5:
      if _pythonMajorVersion < 3:
        pad_len = ord(data[-1])
      else:
        pad_len = data[-1]
      data = data[:-pad_len]
    re